Video encoding method and apparatus and video decoding method and apparatus, based on hierarchical coded block pattern information

ABSTRACT

A method and apparatus for decoding video and a method and apparatus for encoding video are provided. The method for decoding video includes: receiving and parsing a bitstream of encoded video; extracting, from the bitstream, encoded image data of a current picture assigned to a maximum coding unit of the current picture, information regarding a coded depth of the maximum coding unit, information regarding an encoding mode, and coding unit pattern information indicating whether texture information of the maximum coding units has been encoded; and decoding the encoded image data for the maximum coding unit, based on the information regarding the coded depth of the maximum coding unit, the information regarding the encoding mode, and the coding unit pattern information.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 12/856,272, filed on Aug. 13, 2010 in the U.S.Patent and Trademark Office, which claims priority from Korean PatentApplication No. 10-2009-0075337, filed on Aug. 14, 2009 in the KoreanIntellectual Property Office, the contents of which are hereinincorporated by reference in their entireties.

BACKGROUND

1. Field

Exemplary embodiments relate to encoding and decoding video.

2. Description of the Related Art

As hardware for reproducing and storing high resolution or high qualityvideo content is being developed and supplied, a need for a video codecfor effectively encoding or decoding the high resolution or high qualityvideo content is increasing. In a related art video codec, video isencoded according to a limited encoding method based on a macroblockhaving a predetermined size. Also, in the related art video codec, codedblock pattern information is encoded in units of macro blocks.

SUMMARY

Apparatuses and methods consistent with exemplary embodiments provideencoding and decoding video by using information indicating whethertexture information of a coding unit has been encoded and inconsideration of a hierarchical depth.

According to an aspect of an exemplary embodiment, there is provided amethod of decoding video, the method including: receiving and parsing abitstream of encoded video; extracting, from the bitstream, encodedimage data of a current picture assigned to a maximum coding unit of thecurrent picture, information regarding a coded depth of the maximumcoding unit, information regarding an encoding mode, and coding unitpattern information indicating whether texture information of themaximum coding unit has been encoded; and decoding the encoded imagedata for the maximum coding unit, based on the information regarding thecoded depth of the maximum coding unit, the information regarding theencoding mode, and the coding unit pattern information.

The coding unit may be characterized by a maximum size and a depth.

The depth may indicate a number of times a coding unit is hierarchicallysplit, and as the depth deepens, deeper coding units according to depthsmay be split from the maximum coding unit to obtain minimum codingunits.

The depth may be deepened from an upper depth to a lower depth.

As the depth deepens, the number of times the maximum coding unit issplit may increase, and a total number of possible times the maximumcoding unit is split may correspond to a maximum depth.

The maximum size and the maximum depth of the coding unit may bepredetermined.

Coding unit pattern information regarding the maximum coding unit mayinclude at least one of coding unit pattern information corresponding tocoded depth, which is set for a coding unit corresponding to the codeddepth, and hierarchical coding unit pattern information according totransformation depths, which indicates whether hierarchical coding unitpattern information regarding a lower depth has been encoded.

If the coding unit pattern information regarding the coding unitsaccording to the coded depths indicates that the texture information ofthe maximum coding units has been encoded, the decoding the encodedimage data may include extracting transformation unit patterninformation indicating whether texture information of at least onetransformation unit included in the coding unit corresponding to thecoded depth has been encoded.

If the transformation unit pattern information indicates that textureinformation of the transformation unit has been encoded, the decodingthe encoded image data may include decoding the encoded textureinformation.

If the transformation unit pattern information indicates that textureinformation of the transformation unit has not been encoded, thedecoding the encoded image data may include decoding the transformationunit by using information regarding transformation units adjacent to thetransformation unit.

The coding unit pattern information corresponding to coded depth may beextracted according to color components of the image data.

If the coding unit corresponding to the coded depth includes at leastfour transformation units, the first group may be divided into fourlower groups, and predetermined-bit coding unit pattern informationcorresponding to the coded depth may further be extracted for each ofthe four lower groups.

According to an aspect of another exemplary embodiment, there isprovided a method of encoding video, the method including: splitting acurrent picture of the video into a maximum coding unit; determining acoded depth to output a final encoding result according to at least onesplit region, which is obtained by splitting a region of the maximumcoding unit according to depths, by encoding the at least one splitregion, based on a depth that deepens in proportion to a number of timesthe region of the maximum coding unit is split; and outputting imagedata that is the final encoding result according to the at least onesplit region, and encoding and outputting information about the codeddepth and a prediction mode and coding unit pattern information one ofthe maximum coding unit, wherein the coding unit pattern informationindicates whether texture information of the maximum coding unit hasbeen encoded.

The outputting of the image data may include setting and encoding thecoding unit pattern information, based on whether all transformationcoefficients of the texture information of the maximum coding unit are0.

The outputting of the image data may include setting and encoding thecoding unit pattern information corresponding to coded depth, accordingto the coded depth of the maximum coding unit, based on whether alltransformation coefficients of the coding unit corresponding to thecoded depths are 0.

If hierarchical coding unit pattern information and texture informationregarding a coding unit corresponding to an upper depth of a currentdepth are not encoded, then the outputting of the image data may includesetting and encoding hierarchical coding unit pattern information froman uppermost depth to the current depth.

The method may further include determining whether at least one of thecoding unit pattern information corresponding to coded depth and thehierarchical coding unit pattern information for each of the at leastone transformation depth, is to be used with respect to at least one ofthe current picture, a slice, and the maximum coding unit.

The outputting of the coding unit pattern information may includedetermining whether transformation unit pattern information is to be setfor a transformation unit included in a coding unit corresponding to thecoded depth, based on coding unit pattern information regarding themaximum coding unit, wherein the transformation unit pattern informationindicates whether texture information of the transformation unit hasbeen encoded.

According to an aspect of another exemplary embodiment, there isprovided an apparatus for decoding video, the apparatus including: areceiver which receives and parses a bitstream of encoded video; anextractor which extracts, from the bitstream, encoded image data of acurrent picture assigned to a maximum coding unit, information regardinga coded depth of the maximum coding unit, information regarding anencoding mode, and coding unit pattern information indicating whethertexture information of the maximum coding unit has been encoded; and animage data decoder which decodes the encoded image data in the maximumcoding unit, based on the information regarding thee coded depth of themaximum coding unit, the information regarding the encoding mode, andthe coding unit pattern information.

According to an aspect of another exemplary embodiment, there isprovided an apparatus for encoding video, the apparatus including: amaximum coding unit splitter which splits a current picture into amaximum coding unit; a coding unit determiner which determines a codeddepth to output a final encoding result according to at least one splitregion, which is obtained by splitting a region of each of the maximumcoding unit according to depths, by encoding the at least one splitregion, based on a depth that deepens in proportion to a number of timesthe region of the maximum coding unit is split; and an output unit whichoutputs image data that is the final encoding result according to the atleast one split region, and which encodes and outputs information aboutthe coded depth and an encoding mode and coding unit pattern informationof the maximum coding unit, wherein the coding unit pattern informationindicates whether texture information of each of the at least onemaximum coding unit has been encoded.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon acomputer program for executing the above method of decoding video.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon acomputer program for executing the above method of encoding video.

According to an aspect of another exemplary embodiment, there isprovided a method of decoding video, the method including: extracting,from a bitstream of encoded video, encoded image data of a currentpicture assigned to a maximum coding unit of the current picture,information regarding a coded depth of the maximum coding unit, andcoding unit pattern information indicating whether texture informationof the maximum coding unit has been encoded; and decoding the encodedimage data for the maximum coding unit, based on the extractedinformation regarding the coded depth of the maximum coding unit, andthe coding unit pattern information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become more apparent by describingin detail exemplary embodiments thereof with reference to the attacheddrawings in which:

FIG. 1 is a block diagram of a video encoding apparatus according to anexemplary embodiment;

FIG. 2 is a block diagram of a video decoding apparatus according to anexemplary embodiment;

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment;

FIG. 4 is a block diagram of an image encoder based on coding unitsaccording to an exemplary embodiment;

FIG. 5 is a block diagram of an image decoder based on coding unitsaccording to an exemplary embodiment;

FIG. 6 is a diagram illustrating deeper coding units according todepths, and partitions according to an exemplary embodiment;

FIG. 7 is a diagram for describing a relationship between a coding unitand transformation units, according to an exemplary embodiment;

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment;

FIG. 9 is a diagram of deeper coding units according to depths,according to an exemplary embodiment;

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units, prediction units, and transformation units, according toan exemplary embodiment;

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information according to an exemplaryembodiment;

FIG. 14 is a flowchart illustrating a method of encoding a video,according to an exemplary embodiment;

FIG. 15 is a flowchart illustrating a method of decoding a video,according to an exemplary embodiment;

FIG. 16 is a block diagram of a video encoding apparatus using codingunit pattern information, according to an exemplary embodiment;

FIG. 17 is a block diagram of a video decoding apparatus using codingunit pattern information, according to an exemplary embodiment;

FIGS. 18 to 20 are block diagrams illustrating coding unit patterninformation corresponding to a coded depth when a coding unitcorresponding to a coded depth includes one transformation unit,according to exemplary embodiments;

FIGS. 21 to 23 illustrate coding unit pattern information correspondingto a coded depth when a coding unit corresponding to the coded depthincludes four transformation units, according to exemplary embodiments;

FIGS. 24 to 26 illustrate coding unit pattern information correspondingto a coded depth when a coding unit corresponding to the coded depthincludes a plurality of transformation units, according to exemplaryembodiments;

FIG. 27 is a diagram illustrating hierarchical coding unit patterninformation according to an exemplary embodiment;

FIG. 28 is a flowchart illustrating a method of encoding video by usingcoding unit pattern information, according to an exemplary embodiment;and

FIG. 29 is a flowchart illustrating a method of decoding video by usingcoding unit pattern information, according to an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a method and apparatus for encoding video and a method andapparatus for decoding video according to one or more exemplaryembodiments will be described with reference to the accompanyingdrawings. Particularly, video encoding and decoding performed based oncoding units according to a tree structure including spatiallyindependent, hierarchical data units according to one or more exemplaryembodiments will be described with reference to FIGS. 1 to 15. Also,video encoding and decoding performed using coding unit patterninformation regarding a coding unit according to such a tree structureaccording to one or more exemplary embodiments will be described indetail with reference to FIGS. 16 to 29. In the present specification,it is understood that expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

In the present specification, a coding unit is an encoding data unit inwhich image data is encoded at an encoder side and an encoded data unitin which the encoded image data is decoded at a decoder side, accordingto exemplary embodiments. Also, a coded depth indicates a depth where acoding unit is encoded.

In the present specification, an ‘image’ may denote a still image for avideo or a moving image, that is, the video itself.

A method and apparatus for encoding video and a method and apparatus fordecoding video, according to one or more exemplary embodiments, will bedescribed with reference to FIGS. 1 to 15.

FIG. 1 is a block diagram of a video encoding apparatus 100 according toan exemplary embodiment. Referring to FIG. 1, the video encodingapparatus 100 includes a maximum coding unit splitter 110, a coding unitdeterminer 120, and an output unit 130.

The maximum coding unit splitter 110 may split a current picture basedon a maximum coding unit for the current picture of an image. If thecurrent picture is larger than the maximum coding unit, image data ofthe current picture may be split into the at least one maximum codingunit. The maximum coding unit according to an exemplary embodiment maybe a data unit having a size of 32×32, 64×64, 128×128, 256×256, etc.,wherein a shape of the data unit is a square having a width and heightin squares of 2. The image data may be output to the coding unitdeterminer 120 according to the at least one maximum coding unit.

A coding unit according to an exemplary embodiment may be characterizedby a maximum size and a depth. The depth denotes a number of times thecoding unit is spatially split from the maximum coding unit.Accordingly, as the depth deepens, deeper encoding units according todepths may be split from the maximum coding unit to a minimum codingunit. A depth of the maximum coding unit is an uppermost depth and adepth of the minimum coding unit is a lowermost depth. Since a size of acoding unit corresponding to each depth decreases as the depth of themaximum coding unit deepens, a coding unit corresponding to an upperdepth may include a plurality of coding units corresponding to lowerdepths.

As described above, the image data of the current picture is split intoone or more maximum coding units according to a maximum size of thecoding unit, and each of the maximum coding units may include deepercoding units that are split according to depths. Since the maximumcoding unit according to an exemplary embodiment is split according todepths, the image data of a spatial domain included in the maximumcoding unit may be hierarchically classified according to depths.

A maximum depth and maximum size of a coding unit, which limit the totalnumber of times a height and width of the maximum coding unit arehierarchically split, may be predetermined.

The coding unit determiner 120 encodes at least one split regionobtained by splitting a region of the maximum coding unit according todepths, and determines a depth to output a finally encoded image dataaccording to the at least one split region. For example, the coding unitdeterminer 120 determines a coded depth by encoding the image data inthe deeper coding units according to depths, according to the maximumcoding unit of the current picture, and selecting a depth having theleast encoding errors. Thus, the encoded image data of the coding unitcorresponding to the determined coded depth is output by the coding unitdeterminer 120. Also, the coding units corresponding to the coded depthmay be regarded as encoded coding units.

The determined coded depth and the encoded image data according to thedetermined coded depth are output to the output unit 130.

The image data in the maximum coding unit is encoded based on the deepercoding units corresponding to at least one depth equal to or below themaximum depth, and results of encoding the image data are compared basedon each of the deeper coding units. A depth having the least encodingerrors may be selected after comparing encoding errors of the deepercoding units. At least one coded depth may be selected for each maximumcoding unit.

The size of the maximum coding unit is split as a coding unit ishierarchically split according to depths, and as the number of codingunits increases. Also, even if coding units correspond to the same depthin one maximum coding unit, it is determined whether to split each ofthe coding units corresponding to the same depth to a lower depth bymeasuring an encoding error of the image data of each coding unit,separately. Accordingly, even when image data is included in one maximumcoding unit, the image data is split to regions according to the depthsand the encoding errors may differ according to regions in the onemaximum coding unit. Thus, the coded depths may differ according toregions in the image data. Therefore, one or more coded depths may bedetermined in one maximum coding unit, and the image data of the maximumcoding unit may be divided according to coding units of at least onecoded depth.

Accordingly, the coding unit determiner 120 may determine coding unitshaving a tree structure included in the maximum coding unit. The codingunits having a tree structure according to an exemplary embodimentinclude coding units corresponding to a depth determined to be the codeddepth, from among all deeper coding units included in the maximum codingunit. A coding unit of a coded depth may be hierarchically determinedaccording to depths in the same region of the maximum coding unit, andmay be independently determined in different regions. Similarly, a codeddepth in a current region may be independently determined from a codeddepth in another region.

A maximum depth according to an exemplary embodiment is an index relatedto a number of splitting times from a maximum coding unit to a minimumcoding unit. A first maximum depth according to an exemplary embodimentmay denote a total number of splitting times from the maximum codingunit to the minimum coding unit. A second maximum depth according to anembodiment of the present invention may denote a total number of depthlevels from the maximum coding unit to the minimum coding unit. Forexample, when a depth of the maximum coding unit is 0, a depth of acoding unit, in which the maximum coding unit is split once, may be setto 1, and a depth of a coding unit, in which the maximum coding unit issplit twice, may be set to 2. Here, if the minimum coding unit is acoding unit in which the maximum coding unit is split four times, 5depth levels of depths 0, 1, 2, 3 and 4 exist. In this case, the firstmaximum depth may be set to 4, and the second maximum depth may be setto 5.

Prediction encoding and transformation may be performed according to themaximum coding unit. The prediction encoding and the transformation mayalso be performed based on the deeper coding units according to a depthequal to, or depths less than, the maximum depth, according to themaximum coding unit. Transformation may be performed according to amethod of orthogonal transformation or integer transformation.

Since the number of deeper coding units increases whenever the maximumcoding unit is split according to depths, encoding including theprediction encoding and the transformation may be performed on all ofthe deeper coding units generated as the depth deepens. For convenienceof description, the prediction encoding and the transformation will nowbe described based on a coding unit of a current depth, in a maximumcoding unit.

The video encoding apparatus 100 may variously select a size or shape ofa data unit for encoding the image data. In order to encode the imagedata, operations, such as prediction encoding, transformation, andentropy encoding, are performed, and at this time, the same data unitmay be used for all operations or different data units may be used foreach operation.

For example, the video encoding apparatus 100 may select not only acoding unit for encoding the image data, but also a data unit differentfrom the coding unit so as to perform the prediction encoding on theimage data in the coding unit.

In order to perform the prediction encoding in the maximum coding unit,the prediction encoding may be performed based on a coding unitcorresponding to a coded depth, i.e., based on a coding unit that is nolonger split to coding units corresponding to a lower depth.Hereinafter, the coding unit that is no longer split and becomes a basisunit for the prediction encoding will be referred to as a predictionunit. A partition obtained by splitting the prediction unit may includea prediction unit or a data unit obtained by splitting at least one of aheight and a width of the prediction unit.

For example, when a coding unit of 2N×2N (where N is a positive integer)is no longer split and becomes a prediction unit of 2N×2N, a size of apartition may be 2N×2N, 2N×N, N×2N, or N×N. Examples of a partition typeinclude symmetrical partitions that are obtained by symmetricallysplitting a height or a width of the prediction unit, partitionsobtained by asymmetrically splitting the height or the width of theprediction unit (such as 1:n or n:1), partitions that are obtained bygeometrically splitting the prediction unit, and partitions havingarbitrary shapes.

A prediction mode of the prediction unit may be at least one of an intramode, a inter mode, and a skip mode. For example, the intra mode or theinter mode may be performed on the partition of 2N×2N, 2N×N, N×2N, orN×N. Also, the skip mode may be performed only on the partition of2N×2N. The encoding is independently performed on one prediction unit ina coding unit, thereby selecting a prediction mode having a leastencoding error.

The video encoding apparatus 100 may also perform the transformation onthe image data in a coding unit based not only on the coding unit forencoding the image data, but also based on a data unit that is differentfrom the coding unit.

In order to perform the transformation in the coding unit, thetransformation may be performed based on a data unit having a sizesmaller than or equal to the coding unit. For example, the data unit forthe transformation may include a data unit for an intra mode and a dataunit for an inter mode.

A data unit used as a base of the transformation will hereinafter bereferred to as a transformation unit. A transformation depth indicatinga number of splitting times to reach the transformation unit bysplitting a height and a width of the coding unit may also be set in thetransformation unit. For example, in a current coding unit of 2N×2N, atransformation depth may be 0 when a size of a transformation unit isalso 2N×2N, may be 1 when each of the height and the width of thecurrent coding unit is split into two equal parts, totally split into 4̂1transformation units, and the size of the transformation unit is thusN×N, and may be 2 when each of the height and the width of the currentcoding unit is split into four equal parts, totally split into 4̂2transformation units, and the size of the transformation unit is thusN/2×N/2. For example, the transformation unit may be set according to ahierarchical tree structure, in which a transformation unit of an uppertransformation depth is split into four transformation units of a lowertransformation depth according to hierarchical characteristics of atransformation depth.

Similar to the coding unit, the transformation unit in the coding unitmay be recursively split into smaller sized regions, so that thetransformation unit may be determined independently in units of regions.Thus, residual data in the coding unit may be divided according to thetransformation having the tree structure according to transformationdepths.

Encoding information according to coding units corresponding to a codeddepth uses not only information about the coded depth, but alsoinformation about information related to prediction encoding andtransformation. Accordingly, the coding unit determiner 120 not onlydetermines a coded depth having a minimum encoding error, but alsodetermines a partition type in a prediction unit, a prediction modeaccording to prediction units, and a size of a transformation unit fortransformation.

Coding units according to a tree structure in a maximum coding unit anda method of determining a partition, according to one or more exemplaryembodiments, will be described in detail later with reference to FIGS. 3through 12.

The coding unit determiner 120 may measure an encoding error of deepercoding units according to depths by using Rate-Distortion Optimizationbased on Lagrangian multipliers.

The output unit 130 outputs the image data of the maximum coding unit,which is encoded based on the at least one coded depth determined by thecoding unit determiner 120, and information about the encoding modeaccording to the coded depth, in a bitstream. The encoded image data maybe obtained by encoding residual data of an image. The information aboutthe encoding mode according to coded depth may include at least one ofinformation about the coded depth, information about the partition typein the prediction unit, the prediction mode, and the size of thetransformation unit.

The information about the coded depth may be defined by using splitinformation according to depths, which indicates whether encoding isperformed on coding units of a lower depth instead of a current depth.If the current depth of the current coding unit is the coded depth,image data in the current coding unit is encoded and output, and thusthe split information may be defined not to split the current codingunit to a lower depth. Alternatively, if the current depth of thecurrent coding unit is not the coded depth, the encoding is performed onthe coding unit of the lower depth. Thus, the split information may bedefined to split the current coding unit to obtain the coding units ofthe lower depth.

If the current depth is not the coded depth, encoding is performed onthe coding unit that is split into the coding unit of the lower depth.Since at least one coding unit of the lower depth exists in one codingunit of the current depth, the encoding is repeatedly performed on eachcoding unit of the lower depth. Thus, the encoding may be recursivelyperformed for the coding units having the same depth.

Since the coding units having a tree structure are determined for onemaximum coding unit, and information about at least one encoding mode isdetermined for a coding unit of a coded depth, information about atleast one encoding mode may be determined for one maximum coding unit.Also, a coded depth of the image data of the maximum coding unit may bedifferent according to locations since the image data is hierarchicallysplit according to depths. Thus, information about the coded depth andthe encoding mode may be set for the image data.

Accordingly, the output unit 130 may assign encoding information about acorresponding coded depth and an encoding mode to at least one of thecoding unit, the prediction unit, and a minimum unit included in themaximum coding unit.

The minimum unit according to an exemplary embodiment may be arectangular data unit obtained by splitting the minimum coding unithaving the lowermost depth by 4. Alternatively, the minimum unit may bea maximum rectangular data unit that may be included in all of thecoding units, prediction units, partition units, and transformationunits included in the maximum coding unit.

For example, the encoding information output through the output unit 130may be classified into encoding information according to coding units,and encoding information according to prediction units. The encodinginformation according to the coding units may include at least one ofinformation about the prediction mode and information about a size ofthe partitions. The encoding information according to the predictionunits may include at least one of information about an estimateddirection of an inter mode, information about a reference image index ofthe inter mode, information about a motion vector, information about achroma component of an intra mode, and information about aninterpolation method of the intra mode. Also, information about amaximum size of the coding unit defined according to pictures, slices,or groups of pictures (GOPs), and information about a maximum depth maybe inserted into a Sequence Parameter Set (SPS) or a header of abitstream.

In the video encoding apparatus 100, the deeper coding unit may be acoding unit obtained by dividing at least one of a height and a width ofa coding unit of an upper depth, which is one layer above, by two. Inother words, when the size of the coding unit of the current depth is2N×2N, the size of the coding unit of the lower depth may be N×N. Also,the coding unit of the current depth having the size of 2N×2N mayinclude 4 of the coding units of the lower depth.

Accordingly, the video encoding apparatus 100 may form the coding unitshaving the tree structure by determining coding units having an optimumshape and an optimum size for each maximum coding unit, based on thesize of the maximum coding unit and the maximum depth determinedconsidering characteristics of the current picture. Also, since encodingmay be performed on each maximum coding unit by using any of variousprediction modes and transformations, an optimum encoding mode may bedetermined considering characteristics of the coding unit of variousimage sizes.

Thus, if an image having a high resolution or a large data amount isencoded in a related art macroblock, a number of macroblocks per pictureexcessively increases. Accordingly, a number of pieces of compressedinformation generated for each macroblock increases, and thus it isdifficult to transmit the compressed information and data compressionefficiency decreases. However, by using the video encoding apparatus 100according to an exemplary embodiment, image compression efficiency maybe increased since a coding unit is adjusted while consideringcharacteristics of an image while increasing a maximum size of a codingunit while considering a size of the image.

FIG. 2 is a block diagram of a video decoding apparatus 200, accordingto an exemplary embodiment. Referring to FIG. 2, the video decodingapparatus 200 includes a receiver 210, an image data and encodinginformation extractor 220, and an image data decoder 230. Definitions ofvarious terms, such as a coding unit, a depth, a prediction unit, atransformation unit, and information about various encoding modes, forvarious operations of the video decoding apparatus 200 are the same orsimilar to those described above with reference to FIG. 1 and the videoencoding apparatus 100.

The receiver 210 receives and parses a bitstream of an encoded video.The image data and encoding information extractor 220 extracts encodedimage data for each coding unit from the parsed bitstream, wherein thecoding units have a tree structure according to each maximum codingunit, and outputs the extracted image data to the image data decoder230. The image data and encoding information extractor 220 may extractinformation about a maximum size of a coding unit of a current picturefrom a header corresponding to the current picture or an SPS.

Also, the image data and encoding information extractor 220 extractsinformation about a coded depth and an encoding mode for the codingunits having a tree structure according to each maximum coding unit,from the parsed bitstream. The extracted information about the codeddepth and the encoding mode is output to the image data decoder 230.Thus, the image data in a bit stream is split into the maximum codingunit so that the image data decoder 230 decodes the image data for eachmaximum coding unit.

The information about the coded depth and the encoding mode according tothe maximum coding unit may be set for information about at least onecoding unit corresponding to the coded depth. Furthermore, theinformation about the encoding mode may include at least one ofinformation about a partition type of a corresponding coding unitcorresponding to the coded depth, information about a prediction mode,and a size of a transformation unit. Also, splitting informationaccording to depths may be extracted as the information about the codeddepth.

The information about the coded depth and the encoding mode according toeach maximum coding unit extracted by the image data and encodinginformation extractor 220 is information about a coded depth and anencoding mode determined to generate a minimum encoding error when anencoder, such as the video encoding apparatus 100, repeatedly performsencoding for each deeper coding unit according to depths according toeach maximum coding unit. Accordingly, the video decoding apparatus 200may restore an image by decoding the image data according to a codeddepth and an encoding mode that generates the minimum encoding error.

Since encoding information about the coded depth and the encoding modemay be assigned to a predetermined data unit from among a correspondingcoding unit, a prediction unit, and a minimum unit, the image data andencoding information extractor 220 may extract the information about thecoded depth and the encoding mode according to the predetermined dataunits. The predetermined data units to which the same information aboutthe coded depth and the encoding mode is assigned may be inferred to bethe data units included in the same maximum coding unit.

The image data decoder 230 restores the current picture by decoding theimage data in each maximum coding unit based on the information aboutthe coded depth and the encoding mode according to the maximum codingunits. In other words, the image data decoder 230 may decode the encodedimage data based on the extracted information about the partition type,the prediction mode, and the transformation unit for each coding unitfrom among the coding units having the tree structure included in eachmaximum coding unit. A decoding process may include at least one of aprediction including intra prediction and motion compensation, and aninverse transformation. Inverse transformation may be performedaccording to method of inverse orthogonal transformation or inverseinteger transformation.

The image data decoder 230 may perform intra prediction or motioncompensation according to a partition and a prediction mode of eachcoding unit, based on the information about the partition type and theprediction mode of the prediction unit of the coding unit according tocoded depths.

Also, the image data decoder 230 may perform inverse transformationaccording to each transformation unit in the coding unit, based on theinformation about the size of the transformation unit of the coding unitaccording to coded depths, so as to perform the inverse transformationaccording to maximum coding units.

The image data decoder 230 may determine at least one coded depth of acurrent maximum coding unit by using split information according todepths. If the split information indicates that image data is no longersplit in the current depth, the current depth is a coded depth.Accordingly, the image data decoder 230 may decode encoded data of atleast one coding unit corresponding to each coded depth in the currentmaximum coding unit by using the information about the partition type ofthe prediction unit, the prediction mode, and the size of thetransformation unit for each coding unit corresponding to the codeddepth, and output the image data of the current maximum coding unit.

In other words, data units including the encoding information includingthe same split information may be gathered by observing the encodinginformation set assigned for the predetermined data unit from among thecoding unit, the prediction unit, and the minimum unit. Moreover, thegathered data units may be considered to be one data unit to be decodedby the image data decoder 230 in the same encoding mode.

The video decoding apparatus 200 may obtain information about at leastone coding unit that generates the minimum encoding error when encodingis recursively performed for each maximum coding unit, and may use theinformation to decode the current picture. In other words, the codingunits having the tree structure determined to be the optimum codingunits in each maximum coding unit may be decoded. Also, a maximum sizeof the coding unit may be determined considering resolution and anamount of image data.

Accordingly, even if image data has a high resolution and a large amountof data, the image data may be efficiently decoded and restored by usinga size of a coding unit and an encoding mode, which are adaptivelydetermined according to characteristics of the image data, by usinginformation about an optimum encoding mode received from an encoder.

A method of determining coding units having a tree structure, aprediction unit, and a transformation unit, according to one or moreexemplary embodiments will now be described with reference to FIGS. 3through 13.

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment. A size of a coding unit may be expressed inwidth×height, and may be 64×64, 32×32, 16×16, and 8×8, though it isunderstood that another exemplary embodiment is not limited thereto. Acoding unit of 64×64 may be split into partitions of 64×64, 64×32,32×64, or 32×32, a coding unit of 32×32 may be split into partitions of32×32, 32×16, 16×32, or 16×16, a coding unit of 16×16 may be split intopartitions of 16×16, 16×8, 8×16, or 8×8, and a coding unit of 8×8 may besplit into partitions of 8×8, 8×4, 4×8, or 4×4.

Referring to FIG. 3, first video data 310 has a resolution is 1920×1080,a maximum size of a coding unit of 64, and a maximum depth of 2. Secondvideo data 320 has a resolution of 1920×1080, a maximum size of a codingunit of 64, and a maximum depth of 3. Third video data 330 has aresolution of 352×288, a maximum size of a coding unit of 16, and amaximum depth of 1. The maximum depth shown in FIG. 3 denotes a totalnumber of splits from a maximum coding unit to a minimum decoding unit.

If a resolution is high or a data amount is large, a maximum size of acoding unit may be large so as to not only increase encoding efficiencybut also to accurately reflect characteristics of an image. Accordingly,the maximum size of the coding units of the first and second video data310 and 320 having a higher resolution than the third video data 330 maybe 64.

Since the maximum depth of the first video data 310 is 2, coding units315 of the first video data 310 may include a maximum coding unit havinga long axis size of 64, and coding units having long axis sizes of 32and 16 since depths are deepened to two layers by splitting the maximumcoding unit twice. Meanwhile, since the maximum depth of the third videodata 330 is 1, coding units 335 of the third video data 330 may includea maximum coding unit having a long axis size of 16, and coding unitshaving a long axis size of 8 since depths are deepened to one layer bysplitting the maximum coding unit once.

Since the maximum depth of the second video data 320 is 3, coding units325 of the second video data 320 may include a maximum coding unithaving a long axis size of 64, and coding units having long axis sizesof 32, 16, and 8 since the depths are deepened to 3 layers by splittingthe maximum coding unit three times. As a depth deepens (i.e.,increases), detailed information may be precisely expressed.

FIG. 4 is a block diagram of an image encoder 400 based on coding units,according to an exemplary embodiment. Referring to FIG. 4, the imageencoder 400 performs operations of the coding unit determiner 120 of thevideo encoding apparatus 100 to encode image data. For example, an intrapredictor 410 performs intra prediction on coding units in an intramode, from among a current frame 405, and a motion estimator 420 and amotion compensator 425 perform inter estimation and motion compensation,respectively, on coding units in an inter mode from among the currentframe 405 by using the current frame 405, and a reference frame 495.

Data output from the intra predictor 410, the motion estimator 420, andthe motion compensator 425 is output as a quantized transformationcoefficient through a transformer 430 and a quantizer 440. The quantizedtransformation coefficient is restored as data in a spatial domainthrough an inverse quantizer 460 and an inverse transformer 470. Therestored data in the spatial domain is output as the reference frame 495after being post-processed through a deblocking unit 480 and a loopfiltering unit 490. The quantized transformation coefficient may beoutput as a bitstream 455 through an entropy encoder 450.

In order for the image encoder 400 to be applied in the video encodingapparatus 100, elements of the image encoder 400, i.e., the intrapredictor 410, the motion estimator 420, the motion compensator 425, thetransformer 430, the quantizer 440, the entropy encoder 450, the inversequantizer 460, the inverse transformer 470, the deblocking unit 480, andthe loop filtering unit 490, perform operations based on each codingunit from among coding units having a tree structure while consideringthe maximum depth of each maximum coding unit.

Specifically, the intra predictor 410, the motion estimator 420, and themotion compensator 425 determine partitions and a prediction mode ofeach coding unit from among the coding units having a tree structurewhile considering a maximum size and a maximum depth of a currentmaximum coding unit, and the transformer 430 determines a size of thetransformation unit in each coding unit from among the coding unitshaving a tree structure.

FIG. 5 is a block diagram of an image decoder 500 based on coding units,according to an exemplary embodiment. Referring to FIG. 5, a parser 510parses encoded image data to be decoded and information about encodingused for decoding from a bitstream 505. The encoded image data is outputas inverse quantized data through an entropy decoder 520 and an inversequantizer 530, and the inverse quantized data is restored to image datain a spatial domain through an inverse transformer 540.

An intra predictor 550 performs intra prediction on coding units in anintra mode with respect to the image data in the spatial domain, and amotion compensator 560 performs motion compensation on coding units inan inter mode by using a reference frame 585.

The image data in the spatial domain, which passed through the intrapredictor 550 and the motion compensator 560, may be output as arestored frame 595 after being post-processed through a deblocking unit570 and a loop filtering unit 580. Also, the image data that ispost-processed through the deblocking unit 570 and the loop filteringunit 580 may be output as the reference frame 585.

In order to decode the image data in the image data decoder 230 of thevideo decoding apparatus 200, the image decoder 500 may performoperations that are performed after the parser 510.

In order for the image decoder 500 to be applied in the video decodingapparatus 200, elements of the image decoder 500, i.e., the parser 510,the entropy decoder 520, the inverse quantizer 530, the inversetransformer 540, the intra predictor 550, the motion compensator 560,the deblocking unit 570, and the loop filtering unit 580, performoperations based on coding units having a tree structure for eachmaximum coding unit.

Specifically, the intra prediction 550 and the motion compensator 560perform operations based on partitions and a prediction mode for each ofthe coding units having a tree structure, and the inverse transformer540 performs operations based on a size of a transformation unit foreach coding unit.

FIG. 6 is a diagram illustrating deeper coding units according todepths, and partitions, according to an exemplary embodiment. A videoencoding apparatus 100 according to an exemplary embodiment and a videodecoding apparatus 200 according to an exemplary embodiment usehierarchical coding units so as to consider characteristics of an image.A maximum height, a maximum width, and a maximum depth of coding unitsmay be adaptively determined according to the characteristics of theimage, or may be differently set by a user. Sizes of deeper coding unitsaccording to depths may be determined according to a predeterminedmaximum size of the coding unit.

Referring to FIG. 6, in a hierarchical structure 600 of coding units,according to an exemplary embodiment, the maximum height and the maximumwidth of the coding units are each 64, and the maximum depth is 4. Sincea depth deepens (i.e., increases) along a vertical axis of thehierarchical structure 600, a height and a width of the deeper codingunits are each split. Also, a prediction unit and partitions, which arebases for prediction encoding of each deeper coding unit, are shownalong a horizontal axis of the hierarchical structure 600.

For example, a first coding unit 610 is a maximum coding unit in thehierarchical structure 600, wherein a depth thereof is 0 and a size,i.e., a height by width, thereof is 64×64. The depth deepens along thevertical axis such that the hierarchical structure 600 includes a secondcoding unit 620 having a size of 32×32 and a depth of 1, a third codingunit 630 having a size of 16×16 and a depth of 2, a fourth coding unit640 having a size of 8×8 and a depth of 3, and a fifth coding unit 650having a size of 4×4 and a depth of 4. The fifth coding unit 650 havingthe size of 4×4 and the depth of 4 is a minimum coding unit.

The prediction unit and the partitions of the coding units 610, 620,630, 640, and 650 are arranged along the horizontal axis according toeach depth. In other words, if the first coding unit 610 having the sizeof 64×64 and the depth of 0 is a prediction unit, the prediction unitmay be split into partitions included in the first coding unit 610, i.e.a partition 610 having a size of 64×64, partitions 612 having a size of64×32, partitions 614 having a size of 32×64, or partitions 616 having asize of 32×32.

Similarly, a prediction unit of the second coding unit 620 having thesize of 32×32 and the depth of 1 may be split into partitions includedin the second coding unit 620, i.e. a partition 620 having a size of32×32, partitions 622 having a size of 32×16, partitions 624 having asize of 16×32, and partitions 626 having a size of 16×16.

Similarly, a prediction unit of the third coding unit 630 having thesize of 16×16 and the depth of 2 may be split into partitions includedin the third coding unit 630, i.e. a partition having a size of 16×16included in the third coding unit 630, partitions 632 having a size of16×8, partitions 634 having a size of 8×16, and partitions 636 having asize of 8×8.

Similarly, a prediction unit of the fourth coding unit 640 having thesize of 8×8 and the depth of 3 may be split into partitions included inthe fourth coding unit 640, i.e. a partition having a size of 8×8included in the fourth coding unit 640, partitions 642 having a size of8×4, partitions 644 having a size of 4×8, and partitions 646 having asize of 4×4.

The fifth coding unit 650 having the size of 4×4 and the depth of 4 isthe minimum coding unit and a coding unit of the lowermost depth. Aprediction unit of the fifth coding unit 650 is assigned to a partitionhaving a size of 4×4.

In order to determine the at least one coded depth of the coding unitsof the maximum coding unit 610, the coding unit determiner 120 of thevideo encoding apparatus 100 performs encoding for coding unitscorresponding to each depth included in the maximum coding unit 610.

A number of deeper coding units according to depths including data inthe same range and the same size increases as the depth deepens. Forexample, four coding units corresponding to a depth of 2 are required tocover data that is included in one coding unit corresponding to a depthof 1. Accordingly, in order to compare encoding results of the same dataaccording to depths, the coding unit corresponding to the depth of 1 andfour coding units corresponding to the depth of 2 are each encoded.

In order to perform encoding for a current depth from among the depths,a minimum encoding error may be selected for the current depth byperforming encoding for each prediction unit in the coding unitscorresponding to the current depth, along the horizontal axis of thehierarchical structure 600. Alternatively, the minimum encoding errormay be searched for by comparing the minimum encoding errors accordingto depths, by performing encoding for each depth as the depth deepensalong the vertical axis of the hierarchical structure 600. A depth and apartition having the minimum encoding error in the first coding unit 610may be selected as the coded depth and a partition type of the firstcoding unit 610.

FIG. 7 is a diagram for describing a relationship between a coding unit710 and transformation units 720, according to an exemplary embodiment.A video encoding apparatus 100 according to an exemplary embodiment anda video decoding apparatus 200 according to an exemplary embodimentencodes and decodes, respectively, an image according to coding unitshaving sizes smaller than or equal to a maximum coding unit for eachmaximum coding unit. Sizes of transformation units for transformationduring encoding may be selected based on data units that are not largerthan a corresponding coding unit.

Referring to FIG. 7, for example, in the video encoding apparatus 100,if a size of the coding unit 710 is 64×64, transformation may beperformed by using the transformation units 720 having a size of 32×32.

Also, data of the coding unit 710 having the size of 64×64 may beencoded by performing the transformation on each of the transformationunits having the size of 32×32, 16×16, 8×8, and 4×4, which are smallerthan 64×64, and then a transformation unit having the least codingerrors may be selected.

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment.Referring to FIG. 8, the output unit 130 of a video encoding apparatus100 according to an exemplary embodiment may encode and transmit firstinformation 800 about a partition type, second information 810 about aprediction mode, and third information 820 about a size of atransformation unit for each coding unit corresponding to a coded depth,as information about an encoding mode.

The first information 800 indicates information about a shape of apartition obtained by splitting a prediction unit of a current codingunit, wherein the partition is a data unit for prediction encoding thecurrent coding unit. For example, a current coding unit CU_(—)0 having asize of 2N×2N may be split into any one of a partition 802 having a sizeof 2N×2N, a partition 804 having a size of 2N×N, a partition 806 havinga size of N×2N, and a partition 808 having a size of N×N. Here, thefirst information 800 about a partition type is set to indicate one ofthe partition 804 having a size of 2N×N, the partition 806 having a sizeof N×2N, and the partition 808 having a size of N×N

The second information 810 indicates a prediction mode of eachpartition. For example, the second information 810 may indicate a modeof prediction encoding performed on a partition indicated by the firstinformation 800, i.e., an intra mode 812, an inter mode 814, or a skipmode 816.

The third information 820 indicates a transformation unit to be based onwhen transformation is performed on a current coding unit. For example,the transformation unit may be a first intra transformation unit 822, asecond intra transformation unit 824, a first inter transformation unit826, or a second intra transformation unit 828.

An image data and encoding information extractor 220 of a video decodingapparatus 200 according to an exemplary embodiment may extract and usethe information 800, 810, and 820 for decoding, according to each deepercoding unit

FIG. 9 is a diagram of deeper coding units according to depths,according to an exemplary embodiment. Split information may be used toindicate a change of a depth. The spilt information indicates whether acoding unit of a current depth is split into coding units of a lowerdepth.

Referring to FIG. 9, a prediction unit 910 for prediction encoding acoding unit 900 having a depth of 0 and a size of 2N_(—)0×2N_(—)0 mayinclude partitions of a partition type 912 having a size of2N_(—)0×2N_(—)0, a partition type 914 having a size of 2N_(—)0×N_(—)0, apartition type 916 having a size of N_(—)0×2N_(—)0, and a partition type918 having a size of N_(—)0×N_(—)0. FIG. 9 only illustrates thepartition types 912 through 918 which are obtained by symmetricallysplitting the prediction unit 910, but it is understood that a partitiontype is not limited thereto in another exemplary embodiment. Forexample, according to another exemplary embodiment, the partitions ofthe prediction unit 910 may include asymmetrical partitions, partitionshaving a predetermined shape, and partitions having a geometrical shape.

Prediction encoding is repeatedly performed on one partition having asize of 2N_(—)0×2N_(—)0, two partitions having a size of 2N_(—)0×N_(—)0,two partitions having a size of N_(—)0×2N_(—)0, and four partitionshaving a size of N_(—)0×N_(—)0, according to each partition type. Theprediction encoding in an intra mode and an inter mode may be performedon the partitions having the sizes of 2N_(—)0×2N_(—)0, N_(—)0×2N_(—)0,2N_(—)0×N_(—)0, and N_(—)0×N_(—)0. The prediction encoding in a skipmode is performed only on the partition having the size of2N_(—)0×2N_(—)0.

Errors of encoding including the prediction encoding in the partitiontypes 912 through 918 are compared, and the minimum encoding error isdetermined among the partition types. If an encoding error is smallestin one of the partition types 912 through 916, the prediction unit 910may not be split into a lower depth.

If the encoding error is the smallest in the partition type 918, a depthis changed from 0 to 1 to split the partition type 918 in operation 920,and encoding is repeatedly performed on coding units 930 having a depthof 2 and a size of N_(—)0×N_(—)0 to search for a minimum encoding error.

A prediction unit 940 for prediction encoding the coding unit 930 havinga depth of 1 and a size of 2N_(—)1×2N_(—)1 (=N_(—)0×N_(—)0) may includepartitions of a partition type 942 having a size of 2N_(—)1×2N_(—)1, apartition type 944 having a size of 2N_(—)1×N_(—)1, a partition type 946having a size of N_(—)1×2N_(—)1, and a partition type 948 having a sizeof N_(—)1×N_(—)1.

If an encoding error is the smallest in the partition type 948, a depthis changed from 1 to 2 to split the partition type 948 in operation 950,and encoding is repeatedly performed on coding units 960, which have adepth of 2 and a size of N_(—)2×N_(—)2 to search for a minimum encodingerror.

When a maximum depth is d, split operations according to each depth maybe performed up to when a depth becomes d−1, and split information maybe encoded up to when a depth is one of 0 to d−2. For example, whenencoding is performed up to when the depth is d−1 after a coding unitcorresponding to a depth of d−2 is split in operation 970, a predictionunit 990 for prediction encoding a coding unit 980 having a depth of d−1and a size of 2N_(d−1)×2N_(d−1) may include partitions of a partitiontype 992 having a size of 2N_(d−1)×2N_(d−1), a partition type 994 havinga size of 2N_(d−1)×N_(d−1), a partition type 996 having a size ofN_(d−1)×2N_(d−1), and a partition type 998 having a size ofN_(d−1)×N_(d−1).

Prediction encoding may be repeatedly performed on one partition havinga size of 2N_(d−1)×2N_(d−1), two partitions having a size of2N_(d−1)×N_(d−1), two partitions having a size of N_(d−1)×2N_(d−1), fourpartitions having a size of N_(d−1)×N_(d−1) from among the partitiontypes 992 through 998 to search for a partition type having a minimumencoding error.

Even when the partition type 998 has the minimum encoding error, since amaximum depth is d, a coding unit CU_(d−1) having a depth of d−1 is nolonger split to a lower depth, and a coded depth for the coding units ofa current maximum coding unit 900 is determined to be d−1 and apartition type of the current maximum coding unit 900 may be determinedto be N_(d−1)×N_(d−1). Also, since the maximum depth is d and a minimumcoding unit 980 having a lowermost depth of d−1 is no longer split to alower depth, split information for the minimum coding unit 980 is notset.

A data unit 999 may be considered a minimum unit for the current maximumcoding unit. A minimum unit according to an exemplary embodiment may bea rectangular data unit obtained by splitting a minimum coding unit 980by 4. By performing the encoding repeatedly, a video encoding apparatus100 according to an exemplary embodiment may select a depth having theminimum encoding error by comparing encoding errors according to depthsof the coding unit 900 to determine a coded depth, and set acorresponding partition type and a prediction mode as an encoding modeof the coded depth.

As such, the minimum encoding errors according to depths are compared inall of the depths of 1 through d, and a depth having the least encodingerrors may be determined as a coded depth. At least one of the codeddepth, the partition type of the prediction unit, and the predictionmode may be encoded and transmitted as information about an encodingmode. Also, since a coding unit is split from a depth of 0 to a codeddepth, only split information of the coded depth is set to 0, and splitinformation of depths excluding the coded depth are set to 1.

An image data and encoding information extractor 220 of a video decodingapparatus 200 according to an exemplary embodiment may extract and usethe information about the coded depth and the prediction unit of thecoding unit 900 to decode the partition 912. The video decodingapparatus 200 may determine a depth, in which split information is 0, asa coded depth by using split information according to depths, and useinformation about an encoding mode of the corresponding depth fordecoding.

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units 1010, prediction units 1060, and transformation units 1070,according to an exemplary embodiment.

Referring to FIGS. 10 through 12, the coding units 1010 are coding unitshaving a tree structure, corresponding to coded depths determined by avideo encoding apparatus 100 according to an exemplary embodiment, in amaximum coding unit. The prediction units 1060 are partitions ofprediction units of each of the coding units 1010, and thetransformation units 1070 are transformation units of each of the codingunits 1010.

When a depth of a maximum coding unit is 0 in the coding units 1010,depths of coding units 1012 and 1054 are 1, depths of coding units 1014,1016, 1018, 1028, 1050, and 1052 are 2, depths of coding units 1020,1022, 1024, 1026, 1030, 1032, and 1048 are 3, and depths of coding units1040, 1042, 1044, and 1046 are 4.

In the prediction units 1060, some encoding units 1014, 1016, 1022,1032, 1048, 1050, 1052, and 1054 are obtained by splitting the codingunits of the coding units 1010. For example, partition types in thecoding units 1014, 1022, 1050, and 1054 have a size of 2N×N, partitiontypes in the coding units 1016, 1048, and 1052 have a size of N×2N, anda partition type of the coding unit 1032 has a size of N×N. Predictionunits and partitions of the coding units 1010 are smaller than or equalto each coding unit.

Transformation or inverse transformation is performed on image data ofthe coding unit 1052 in the transformation units 1070 in a data unitthat is smaller than the coding unit 1052. Also, the coding units 1014,1016, 1022, 1032, 1048, 1050, and 1052 in the transformation units 1070are different from those in the prediction units 1060 in terms of sizesand shapes. For example, video encoding and decoding apparatuses 100 and200 according to exemplary embodiments may perform intra prediction,motion estimation, motion compensation, transformation, and inversetransformation individually on a data unit in the same coding unit.

Accordingly, encoding is recursively performed on each of coding unitshaving a hierarchical structure in each region of a maximum coding unitto determine an optimum coding unit, and thus coding units having arecursive tree structure may be obtained. Encoding information mayinclude at least one of split information about a coding unit,information about a partition type, information about a prediction mode,and information about a size of a transformation unit. Table 1 showsexemplary encoding information that may be set by the video encoding anddecoding apparatuses 100 and 200.

TABLE 1 Split Information 0 (Encoding on Coding Unit having Size of2Nx2N and Current Depth of d) Size of Transformation Unit Split SplitPartition Type Information 0 Information 1 Symmetrical Asymmetrical ofof Split Prediction Partition Partition Transformation TransformationInformation Mode Type Type Unit Unit 1 Intra 2Nx2N 2NxnU 2Nx2N NxNRepeatedly Inter 2NxN 2NxnD (Symmetrical Encode Skip Nx2N nLx2N Type)Coding Units (Only NxN nRx2N N/2xN/2 having 2Nx2N) (Asymmetrical LowerDepth Type) of d + 1

An output unit 130 of the video encoding apparatus 100 may output theencoding information about the coding units having a tree structure, andan image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract the encoding information about thecoding units having a tree structure from a received bitstream.

Split information indicates whether a current coding unit is split intocoding units of a lower depth. If split information of a current depth dis 0, a depth in which a current coding unit is no longer split into alower depth is a coded depth, and thus information about a partitiontype, prediction mode, and a size of a transformation unit may bedefined for the coded depth. If the current coding unit is further splitaccording to the split information, encoding is independently performedon four split coding units of a lower depth.

A prediction mode may be one of an intra mode, an inter mode, and a skipmode. The intra mode and the inter mode may be defined in all partitiontypes, and the skip mode may be defined only in a partition type havinga size of 2N×2N.

The information about the partition type may indicate symmetricalpartition types having sizes of 2N×2N, 2N×N, N×2N, and N×N, which areobtained by symmetrically splitting at least one of a height and a widthof a prediction unit, and asymmetrical partition types having sizes of2N×nU, 2N×nD, nL×2N, and nR×2N, which are obtained by asymmetricallysplitting at least one of the height and the width of the predictionunit. The asymmetrical partition types having the sizes of 2N×nU and2N×nD may be respectively obtained by splitting the height of theprediction unit in 1:3 and 3:1, and the asymmetrical partition typeshaving the sizes of nL×2N and nR×2N may be respectively obtained bysplitting the width of the prediction unit in 1:3 and 3:1

The size of the transformation unit may be set to be two types in theintra mode and two types in the inter mode. For example, if splitinformation of the transformation unit is 0, the size of thetransformation unit may be 2N×2N, which is the size of the currentcoding unit. If split information of the transformation unit is 1, thetransformation units may be obtained by splitting the current codingunit. Also, if a partition type of the current coding unit having thesize of 2N×2N is a symmetrical partition type, a size of atransformation unit may be N×N, and if the partition type of the currentcoding unit is an asymmetrical partition type, the size of thetransformation unit may be N/2×N/2.

The encoding information about coding units having a tree structure mayinclude at least one of a coding unit corresponding to a coded depth, aprediction unit, and a minimum unit. The coding unit corresponding tothe coded depth may include at least one of a prediction unit and aminimum unit including the same encoding information.

Accordingly, it is determined whether adjacent data units are includedin the same coding unit corresponding to the coded depth by comparingencoding information of the adjacent data units. Also, a correspondingcoding unit corresponding to a coded depth is determined by usingencoding information of a data unit, and thus a distribution of codeddepths in a maximum coding unit may be determined.

Therefore, if a current coding unit is predicted based on encodinginformation of adjacent data units, encoding information of data unitsin deeper coding units adjacent to the current coding unit may bedirectly referred to and used.

Alternatively, if a current coding unit is predicted based on encodinginformation of adjacent data units, data units adjacent to the currentcoding unit are searched using encoding information of the data units,and the searched adjacent coding units may be referred to for predictingthe current coding unit.

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information of Table 1 according to anexemplary embodiment. Referring to FIG. 13, a maximum coding unit 1300includes coding units 1302, 1304, 1306, 1312, 1314, 1316, and 1318 ofcoded depths. Here, since the coding unit 1318 is a coding unit of acoded depth, split information may be set to 0. Information about apartition type of the coding unit 1318 having a size of 2N×2N may be setto be one of a partition type 1322 having a size of 2N×2N, a partitiontype 1324 having a size of 2N×N, a partition type 1326 having a size ofN×2N, a partition type 1328 having a size of N×N, a partition type 1332having a size of 2N×nU, a partition type 1334 having a size of 2N×nD, apartition type 1336 having a size of nL×2N, and a partition type 1338having a size of nR×2N.

When the partition type is set to be symmetrical, i.e., the partitiontype 1322, 1324, 1326, or 1328, a transformation unit 1342 having a sizeof 2N×2N is set if split information (TU size flag) of a transformationunit is 0, and a transformation unit 1344 having a size of N×N is set ifa TU size flag is 1.

When the partition type is set to be asymmetrical, i.e., the partitiontype 1332, 1334, 1336, or 1338, a transformation unit 1352 having a sizeof 2N×2N is set if a TU size flag is 0, and a transformation unit 1354having a size of N/2×N/2 is set if a TU size flag is 1.

Referring to FIG. 13, the TU size flag is a flag having a value or 0 or1, though it is understood that another exemplary embodiment is notlimited to a 1-bit flag. For example, a transformation unit may behierarchically split having a tree structure while the TU size flagincreases from 0 in another exemplary embodiment.

In this case, the size of a transformation unit that has been actuallyused may be expressed by using a TU size flag of a transformation unit,according to an exemplary embodiment, together with a maximum size andminimum size of the transformation unit. According to an exemplaryembodiment, a video encoding apparatus 100 may encode maximumtransformation unit size information, minimum transformation unit sizeinformation, and a maximum TU size flag. The result of encoding themaximum transformation unit size information, the minimum transformationunit size information, and the maximum TU size flag may be inserted intoan SPS. According to an exemplary embodiment, a video decoding apparatus200 may decode video by using the maximum transformation unit sizeinformation, the minimum transformation unit size information, and themaximum TU size flag.

For example, if the size of a current coding unit is 64×64 and a maximumtransformation unit size is 32×32, the size of a transformation unit maybe 32×32 when a TU size flag is 0, may be 16×16 when the TU size flag is1, and may be 8×8 when the TU size flag is 2.

As another example, if the size of the current coding unit is 32×32 anda minimum transformation unit size is 32×32, the size of thetransformation unit may be 32×32 when the TU size flag is 0. Here, theTU size flag cannot be set to a value other than 0, since the size ofthe transformation unit cannot be less than 32×32.

As another example, if the size of the current coding unit is 64×64 anda maximum TU size flag is 1, the TU size flag may be 0 or 1. Here, theTU size flag cannot be set to a value other than 0 or 1.

Thus, if it is defined that the maximum TU size flag isMaxTransformSizeIndex, a minimum transformation unit size isMinTransformSize, and a transformation unit size is RootTuSize when theTU size flag is 0, then a current minimum transformation unit sizeCurrMinTuSize that can be determined in a current coding unit, may bedefined by Equation (1):

CurrMinTuSize=max(MinTransformSize, RootTuSize/(2̂MaxTransformSizeIndex))  (1).

Compared to the current minimum transformation unit size CurrMinTuSizethat can be determined in the current coding unit, a transformation unitsize RootTuSize when the TU size flag is 0 may denote a maximumtransformation unit size that can be selected in the system. In Equation(1), RootTuSize/(2̂MaxTransformSizeIndex) denotes a transformation unitsize when the transformation unit size RootTuSize, when the TU size flagis 0, is split a number of times corresponding to the maximum TU sizeflag, and MinTransformSize denotes a minimum transformation size. Thus,a smaller value from among RootTuSize/(2̂MaxTransformSizeIndex) andMinTransformSize may be the current minimum transformation unit sizeCurrMinTuSize that can be determined in the current coding unit.

According to an exemplary embodiment, the maximum transformation unitsize RootTuSize may vary according to the type of a prediction mode. Forexample, if a current prediction mode is an inter mode, then RootTuSizemay be determined by using Equation (2) below. In Equation (2),MaxTransformSize denotes a maximum transformation unit size, and PUSizedenotes a current prediction unit size:

RootTuSize=min(MaxTransformSize, PUSize)   (2).

That is, if the current prediction mode is the inter mode, thetransformation unit size RootTuSize when the TU size flag is 0 may be asmaller value from among the maximum transformation unit size and thecurrent prediction unit size:

If a prediction mode of a current partition unit is an intra mode,RootTuSize may be determined by using Equation (3) below. In Equation(3), PartitionSize denotes the size of the current partition unit:

RootTuSize=min(MaxTransformSize, PartitionSize)   (3).

That is, if the current prediction mode is the intra mode, thetransformation unit size RootTuSize when the TU size flag is 0 may be asmaller value from among the maximum transformation unit size and thesize of the current partition unit.

However, the current maximum transformation unit size RootTuSize thatvaries according to the type of a prediction mode in a partition unit isjust an example, and it is understood that another exemplary embodimentis not limited thereto.

FIG. 14 is a flowchart illustrating a method of encoding a video,according to an exemplary embodiment. Referring to FIG. 14, in operation1210, a current picture is split into at least one maximum coding unit.A maximum depth indicating a total number of possible splitting timesmay be predetermined.

In operation 1220, a coded depth to output a final encoding resultaccording to at least one split region, which is obtained by splitting aregion of each maximum coding unit according to depths, is determined byencoding the at least one split region, and a coding unit according to atree structure is determined.

The maximum coding unit is spatially split whenever the depth deepens,and thus is split into coding units of a lower depth. Each coding unitmay be split into coding units of another lower depth by being spatiallysplit independently from adjacent coding units. Encoding is repeatedlyperformed on each coding unit according to depths.

Also, a transformation unit according to partition types having aminimum encoding error is determined for each deeper coding unit. Inorder to determine a coded depth having the minimum encoding error ineach maximum coding unit, encoding errors may be measured and comparedin all deeper coding units according to depths.

In operation 1230, encoded image data corresponding to the finalencoding result according to the coded depth is output for each maximumcoding unit, with encoding information about the coded depth and anencoding mode. The information about the encoding mode may include atleast one of information about a coded depth or split information,information about a partition type of a prediction unit, a predictionmode, and a size of a transformation unit. The encoding informationabout the encoding mode may be transmitted to a decoder with the encodedimage data.

FIG. 15 is a flowchart illustrating a method of decoding a video,according to an exemplary embodiment. Referring to FIG. 15, in operation1310, a bitstream of an encoded video is received and parsed.

In operation 1320, encoded image data of a current picture assigned to amaximum coding unit, and information about a coded depth and an encodingmode according to maximum coding units are extracted from the parsedbitstream. The coded depth of each maximum coding unit is a depth havinga minimum encoding error in each maximum coding unit. In encoding eachmaximum coding unit, the image data is encoded based on at least onedata unit obtained by hierarchically splitting the maximum coding unitaccording to depths.

According to the information about the coded depth and the encodingmode, the maximum coding unit may be split into coding units having atree structure. Each of the coding units having the tree structure isdetermined as a coding unit corresponding to a coded depth, and isoptimally encoded as to output the least encoding errors. Accordingly,encoding and decoding efficiency of an image may be improved by decodingeach piece of encoded image data in the coding units after determiningat least one coded depth according to coding units.

In operation 1330, the image data of each maximum coding unit is decodedbased on the information about the coded depth and the encoding modeaccording to the maximum coding units. For example, the decoded imagedata may be reproduced by a reproducing apparatus, stored in a storagemedium, or transmitted through a network.

Now, video encoding and decoding performed using coding unit patterninformation regarding a coding unit according to a tree structure,according to another exemplary embodiment of, will be described indetail with reference to FIGS. 16 to 29.

FIG. 16 is a block diagram of a video encoding apparatus 1400 usingcoding unit pattern information, according to an exemplary embodiment.Referring to FIG. 16, the video encoding apparatus 1400 includes amaximum coding unit splitter 1410, a coded unit determiner 1420, and anoutput unit 1460. The output unit 1460 includes an encoded image dataoutput unit 1430, an encoding information output unit 1440, and a codingunit pattern information output unit 1450.

The maximum coding unit splitter 1410 and the coded unit determiner 1420correspond to the maximum coding unit splitter 110 and the coded unitdeterminer 120 included in the video encoding apparatus 100 illustratedin FIG. 1, respectively. The operations of the encoded image data outputunit 1430 and the encoding information output unit 1440 may be the sameas or similar to at least some of the operations of the output unit 130included in the video encoding apparatus 100 of FIG. 1. An exemplaryembodiment in which the coding unit pattern information output unit 1450encodes coding unit pattern information will now be described.

In the current exemplary embodiment, the maximum coding unit splitter1410 splits a current picture of an image, based on a maximum codingunit for the current picture. The coded unit determiner 1420 determinesat least one coded depth by encoding image data in coding unitsaccording to depths in each maximum coding unit and selecting a depthhaving the least encoding errors. Thus, the coded unit determiner 1420may determine coding units having a tree structure included in eachmaximum coding unit.

The encoded image data output unit 1430 outputs a bitstream of the imagedata encoded according to the coded depth in each maximum coding unit.The encoding information output unit 1440 encodes and outputsinformation regarding encoding modes according to coded depths in eachmaximum coding unit.

The coding unit pattern information output unit 1450 encodes and outputscoding unit pattern information indicating whether texture informationfor each of the maximum coding units has been encoded. The textureinformation includes, for example, at least one of a quantizationparameter, a transformation coefficient, and a transformation index fora data unit.

If the video encoding apparatus 1400 according to the current exemplaryembodiment corresponds to the image encoder 400 of FIG. 4, then motionestimated/compensated data is generated from image data corresponding toa current coding unit by using the intra predictor 410, the motionestimator 420, and the motion compensator 425 of FIG. 4. The motionestimated/compensated data is transformed by the transformer 430 and isthen quantized by the quantizer 440, thereby generating a transformationcoefficient of the current coding unit.

The coding unit pattern information regarding the current coding unitmay be set based on whether all transformation coefficients of thecurrent coding unit are 0. The transformation coefficients of thecurrent coding unit that are set to be encoded according to the codingunit pattern information may be input to the entropy encoder 450 to beoutput in a bitstream.

The coding unit pattern information is used so as to determine whetherencoded texture is to be transmitted when the texture information is notto be encoded in coding units or when the texture information is to beencoded in coding units. For example, if all transformation coefficientsin the coding units are 0, then the coding unit pattern information isset so as to indicate that the texture information is not to be encoded.However, if any one of the transformation coefficients in the codingunit is not 0, then the coding unit pattern information is set so as toindicate that the texture information has been encoded.

According to an exemplary embodiment, examples of the coding unitpattern information include coding unit pattern informationcorresponding to a coded depth, and hierarchical coding unit patterninformation.

The coding unit pattern information corresponding to a coded depth isset for coding units corresponding to at least one coded depth in amaximum coding unit, and indicates whether texture information of acoding unit corresponding to a coded depth has been encoded. Forexample, the coding unit pattern information corresponding to a codeddepth may indicate whether all transformation coefficients in codingunits according to depths up to a coded depth, are 0.

Hierarchical coding unit pattern information is set for at least onetransformation depth, respectively. A transformation depth of a maximumtransformation unit is an uppermost transformation depth, and atransformation unit splits as a transformation depth becomes deeper.Also, a transformation unit of a current transformation depth mayinclude four transformation units, the depths of which are lower by onelayer than the current transformation depth.

Hierarchical coding unit pattern information corresponding to a currenttransformation depth indicates whether hierarchical coding unit patterninformation regarding transformation units of the one-layer lower depthshave been encoded. The coding unit pattern information output unit 1450sets and encodes hierarchical coding unit pattern information for eachof transformation depths ranging from an uppermost transformation depthto a lowermost transformation depth or to a predetermined depth.

For example, hierarchical coding unit pattern information may be set foreach of transformation depths, and texture information of atransformation unit corresponding to the lowermost transformation depthmay be encoded.

A transformation depth of a transformation unit may be linked to a depthand a coded depth of a corresponding coding unit. For example, atransformation depth may be set to be fixedly equal to or lower by onelayer than a depth of a coding unit. Otherwise, a transformation depthmay be set to be different from a depth of a coding unit.

According to an exemplary embodiment, in the video encoding apparatus1400, whether only one of or both the coding unit pattern informationcorresponding to a coded depth and the hierarchical coding unit patterninformation are to be encoded may be selectively set in at least onedata unit selected from among a GOP, a picture, a slice, and a maximumcoding unit.

For example, if both the coding unit pattern information correspondingto a coded depth and the hierarchical coding unit pattern informationare used, then the coding unit pattern information output unit 1450 mayset hierarchical coding unit pattern information for each of depthsranging from an uppermost depth to a current coded depth, and may setand encode coding unit pattern information corresponding to a codeddepth for a coding unit corresponding to the current coded depth.

The coding unit corresponding to the coded depth may include at leastone transformation unit. Transformation unit pattern informationindicating whether texture information has been encoded, may be set forthe at least one transformation unit, respectively. For example, thetransformation unit pattern information indicates whether a currenttransformation unit includes a transformation coefficient other than 0.

When texture information of transformation units is to be encoded, thecoding unit pattern information output unit 1450 may set transformationunit pattern information for each of the transformation units, and mayset and encode coding unit pattern information corresponding to a codeddepth of a coding unit that includes the transformation units.

If all the transformation coefficients in the encoding unit of the codeddepth are not 0, then the encoded image data output unit 1430 may notoutput encoded texture information. According to an exemplaryembodiment, if all transformation units belonging to a coding unitcorresponding to the coded depth do not include transformationcoefficients other than 0, then the coding unit pattern informationoutput unit 1450 does not encode the transformation unit patterninformation for the coding unit corresponding to the coded depth.Rather, the coding unit pattern information output unit 1450 may set andencode coding unit pattern information corresponding to a coded depth,which indicates the texture information of the coding unit correspondingto the coded depth is not to be encoded, for the coding unitcorresponding to the coded depth.

The coding unit pattern information corresponding to the coded depth maybe set according to color components of the image data. For example, thecoding unit pattern information corresponding to the coded depth may beset for both of a luma component and a chroma component, or may be setfor each of the luma component, the chroma component, a first chromacomponent, and a second chroma component (see FIGS. 18 to 26 for a moredetailed description).

Coding unit pattern information to which one or more bits are assignedmay be set in one of coding units according to depths and transformationunits for each of maximum coding units.

FIG. 17 is a block diagram of a video decoding apparatus 1500 usingcoding unit pattern information, according to an exemplary embodiment.Referring to FIG. 17, the video decoding apparatus 1500 includes areceiver 1501, an extractor 1505, and an image data decoder 1540. Theextractor 1505 includes an image data obtaining unit 1510, a encodinginformation extractor 1520, and a coding unit pattern informationextractor 1530.

The receiver 1501 and the image data decoder 1540 correspond to thereceiver 210 and the image data decoder 230 included in the videodecoding apparatus 200 of FIG. 2, respectively. The operations of theimage data obtaining unit 1510, the encoding information extractor 1520,and the image data decoder 1540 are the same as or similar to at leastsome of the operations of the image data and encoding informationextractor 220 of the video decoding apparatus 200 of FIG. 2. A method ofperforming decoding by using coding unit pattern information extractedby the coding unit pattern information extractor 1530 according to anexemplary embodiment will now be described with reference to FIG. 17.

The receiver 1501 receives and parses a bitstream of encoded video. Theextractor 1505 extracts various types of encoding information from theresult of parsing the bitstream. The image data obtaining unit 1510 mayobtain image data that has been encoded in units of maximum codingunits, from the result of parsing the bitstream. The encodinginformation extractor 1520 parses the bitstream and then extractsinformation regarding a coded depth and a encoding mode for each of themaximum coding units, from a header of a current picture.

The coding unit pattern information extractor 1530 extracts coding unitpattern information indicating whether texture information of a maximumcoding unit has been encoded, for each of the maximum coding units. Thecoding unit pattern information extractor 1530 may extract coding unitpattern information corresponding to a coded depth and hierarchicalcoding unit pattern information regarding a current maximum coding unit,as the coding unit pattern information.

Whether only one of or both the coding unit pattern informationcorresponding to a coded depth and the hierarchical coding unit patterninformation are to be extracted may be set in units of a GOP, a picture,a slice, or a maximum coding unit.

For example, one unit of coding unit pattern information correspondingto a coded depth may be extracted with respect to one coding unitaccording to a coded depth, or one unit of hierarchical coding unitpattern information may be extracted with respect to each of depthsranging from an uppermost depth to the coded depth. One unit of thecoding unit pattern information may be predetermined bits. For each ofthe maximum coding units, one or more bits of coding unit patterninformation may be set in either coding units according to depths or atransformation unit. For example, if the coding unit pattern informationis in the form of flags, then one unit of the coding unit patterninformation may be one bit.

The image data decoder 1540 reconstructs the current picture by decodingthe image data that has been encoded in units of maximum coding units,based on the information regarding coded depths and encoding modes ofthe maximum coding units and the coding unit pattern information.

According to an exemplary embodiment, the image data decoder 1540 maycheck at least one coded depth of the current maximum coding unit, andmay detect hierarchical structures of coding units according to depthsof a tree structure included in the current maximum coding unit, basedon the information regarding coded depths and encoding modes of themaximum coding units.

Also, the image data decoder 1540 may decode the encoded image data byperforming an inverse transformation on a transformation coefficientincluded in the texture information of the maximum coding unit extractedby the coding unit pattern information extractor 1530, based on thecoding unit pattern information regarding the maximum coding unit.

If the image data decoder 1540 corresponds to the image decoder 500 ofFIG. 5, then the transformation coefficient included in the textureinformation of coding units may be inversely transformed intotime-domain data by using the inverse quantizer 530 and the inversetransformer 540.

That is, if the coding unit pattern information indicates that thetexture information of the current coding unit has been encodedaccording to the coding unit pattern information, then the image datadecoder 1540 may receive a transformation coefficient that has beenentropy decoded from the entropy decoder 520 of the image decoder 500 ofFIG. 5, and perform inverse transformation on the transformationcoefficient to obtain spatial-domain data. Time-domain data may bereconstructed into a reconstructed frame by using the intra predictor550, the motion compensator 560, the deblocking unit 570, and the loopfiltering unit 580 of the image decoder 500 of FIG. 5.

The coding unit pattern information extractor 1530 may detect at leastone of coding pattern information of a coded depth and hierarchicalcoding pattern information, as coding unit pattern information regardingcoding units according to coded depths for the current maximum codingunit.

If the coding pattern information according to a coded depth isdetected, then the image data decoder 1540 may determine a method ofdecoding the coding unit corresponding to the current coded depth, basedon the detected coding pattern information according to a coded depth.

For example, if it is determined based on the detected coding patterninformation according to a coded depth that texture information of thecoding unit corresponding to the current coded depth has not beenencoded, then the image data decoder 1540 may decode the coding unitcorresponding to the current coded depth by referring to informationregarding a data unit adjacent to the coding unit corresponding to thecurrent coded depth.

Also, if it is determined based on the detected coding patterninformation according to a coded depth that the texture information ofthe coding unit corresponding to the current coded depth has beenencoded, then the image data decoder 1540 may decode the coding unitcorresponding to the current coded depth by performing inversetransformation on a transformation coefficient included in the encodedtexture information of the coding unit corresponding to the currentcoded depth.

Furthermore, if the hierarchical coding pattern information is detected,the image data decoder 1540 may determine whether hierarchical codingpattern information regarding a lower transformation depth of a currenttransformation depth is present, and determine a method of decoding atransformation unit corresponding to the current transformation depthbased on the detected hierarchical coding unit pattern information.

For example, if it is determined based on the detected hierarchicalcoding unit pattern information corresponding to the currenttransformation unit corresponding to the transformation depth thathierarchical coding pattern information regarding the lower depth of thecurrent transformation depth is present, then the image data decoder1540 may check the hierarchical coding pattern information regarding thelower transformation depth. However, if it is determined based on thedetected hierarchical coding unit pattern information corresponding tothe current transformation unit that hierarchical coding patterninformation regarding the lower depth of the current transformationdepth is not present, then the image data decoder 1540 may decode thecurrent transformation unit corresponding to the current transformationdepth.

If both the coding unit pattern information corresponding to a codeddepth and the hierarchical coding unit pattern information are detected,then the image data decoder 1540 may check whether hierarchical codingpattern information regarding a lower transformation depth of thecurrent transformation depth has been encoded, based on the hierarchicalcoding unit pattern information regarding the current transformationdepth.

If it is determined that hierarchical coding pattern informationregarding the lower transformation depth is present, then thehierarchical coding pattern information regarding the lowertransformation depth may be checked. If it is determined based on thehierarchical coding unit pattern information corresponding to thecurrent transformation depth that hierarchical coding patterninformation regarding the lower transformation depth is not present,then the image data decoder 1540 may decode the transformation unitcorresponding to the current transformation depth, based on coding unitpattern information related to the transformation unit corresponding tothe current transformation depth.

Also, if the current transformation depth is a lowermost depth or apreset final depth, then the transformation unit corresponding to thecurrent transformation depth may be set to be decoded regardless ofhierarchical coding pattern information according to transformationdepths. If the transformation unit corresponding to the currenttransformation depth is decoded, then the texture information, e.g., aquantization parameter, a transformation coefficient, a transformationindex, etc., may be decoded.

The coding unit corresponding to the coded depth may include at leastone transformation unit, and may be decoded by performing inversetransformation based on transformation unit pattern information that isset in each of the at least one transformation unit. That is, whethertexture information of a desired transformation unit has been encodedmay be determined based on the transformation unit pattern information.

Thus, if it is determined based on the coding unit pattern informationcorresponding to the coded depth that the coding unit has encodedtexture information, then the image data decoder 1540 checkstransformation unit pattern information of each of transformation unitsof the coding unit.

If it is determined based on the transformation unit pattern informationthat the desired transformation unit has encoded texture information,then the image data decoder 1540 may perform an inverse transformationon a transformation coefficient of the desired transformation unit. Ifit is determined based on the transformation unit pattern informationthat the desired transformation unit does not have encoded textureinformation, then the image data decoder 1540 may decode encoded imagedata of the desired transformation unit by using information regarding atransformation unit adjacent to the desired transformation unit.

If it is determined based on the coding unit pattern informationcorresponding to the coded depth that the desired transformation unitdoes not have encoded texture information, then transformation unitpattern information regarding all transformation units of the desiredcoding unit has not been encoded. In this case, the image data decoder1540 may not detect transformation unit pattern information for each ofthe transformation units of the desired coding unit.

In the video encoding apparatus 1400 and the video decoding apparatus1500 according to exemplary embodiments, coding unit pattern informationor transformation unit pattern information that has been encoded basedon coding units according to tree structures and transformation unitsmay be used. Thus, it is possible to determine whether transformationunit pattern information of each of the transformation units has beenencoded, based on coding unit pattern information that is set for acoding unit having a plurality of transformation unit groups. Since thenumber of coding units is less than that transformation units, settingcoding unit pattern information for each of the coding units reduces theamount of data than when setting transformation unit pattern informationfor each of all the transformation units, thereby improving bittransmission efficiency.

Coding unit pattern information corresponding to a coded depth that isset according to color components of image data according to exemplaryembodiments will now be described with reference to FIGS. 18 to 26. Itis assumed in the following exemplary embodiments that one unit ofcoding unit pattern information is 1 bit, but it is understood thatanother exemplary embodiment is not limited thereto.

FIGS. 18 to 20 are block diagrams illustrating coding unit patterninformation corresponding to a coded depth when a coding unitcorresponding to a coded depth includes one transformation unit,according to one or more exemplary embodiments.

Referring to FIGS. 18 to 20, a first coding unit of color image dataaccording to the YCbCr color standards includes a luma component codingunit 1600, a first chroma component coding unit 1610, and a secondchroma component coding unit 1620 having a second chroma component.

If a transformation unit of the first coding unit is equal to the firstcoding unit in size, then the first coding unit includes only onetransformation unit. Thus, the transformation unit of the first codingunit includes a luma component transformation unit 1605, a first chromacomponent transformation unit 1615, and a second chroma componenttransformation unit 1625. Transformation unit pattern information may beset for each of the luma component transformation unit 1605, the firstchroma component transformation unit 1615, and the second chromacomponent transformation unit 1625.

Referring to FIG. 18, coding unit pattern information corresponding to acoded depth is not additionally encoded for the first coding unit. Inthis case, the coding unit pattern information output unit 1450 of FIG.16 does not output coding unit pattern information corresponding to acoded depth for the first coding unit. The image data decoder 1540 ofFIG. 17 may check only transformation unit pattern information for eachof the luma component transformation unit 1605, the first chromacomponent transformation unit 1615, and the second chroma componenttransformation unit 1625 and perform an inverse transformation ontransformation coefficients of the luma component transformation unit1605, the first chroma component transformation unit 1615, and thesecond chroma component transformation unit 1625, based on the checkingresult, without checking coding unit pattern information correspondingto a coded depth for the first coding unit.

Referring to FIG. 19, 1-bit coding unit pattern informationcorresponding to a coded depth is set for a group 1630 to which a lumacomponent transformation unit 1600, a first chroma componenttransformation unit 1610, and a second chroma component transformationunit 1620 of a first coding unit belong. In this case, the coding unitpattern information output unit 1450 of FIG. 16 outputs the 1-bit codingunit pattern information corresponding to a coded depth for the firstcoding unit.

Referring to FIG. 20, 1-bit coding unit pattern informationcorresponding to a coded depth is set for each of a group 1640 to whicha luma component coding unit 1600 of a first coding unit belongs, and agroup 1650 to which a first chroma component coding unit 1610 and asecond chroma component coding unit 1620 of the first coding unitbelong. In this case, the coding unit pattern information output unit1450 of FIG. 16 outputs a 2-bit coding unit pattern informationcorresponding to a coded depth for the first coding unit.

According to an exemplary embodiment, the image data decoder 1540 ofFIG. 17 may determine whether a desired coding unit includes encodedtexture information by checking either the 1-bit coding unit patterninformation corresponding to a coded depth of FIG. 19 or the 2-bitcoding unit pattern information corresponding to a coded depth of FIG.20, for a first coding unit. If the desired coding unit includes encodedtexture information, then the image data decoder 1540 of FIG. 17 maycheck transformation unit pattern information of a correspondingtransformation unit and perform inverse transformation on correspondingtransformation coefficients, based on the checking result.

FIGS. 21 to 23 illustrate coding unit pattern information correspondingto a coded depth when a coding unit corresponding to the coded depthincludes four transformation units, according to exemplary embodiments.Referring to FIGS. 21 to 23, a second coding unit of color image dataaccording to the YCbCr color standards includes a luma component codingunit 1700, a first chroma component coding unit 1710, and a secondchroma component coding unit 1720.

If the second coding unit includes four transformation units, then eachof the coding units of the second coding unit, which are categorizedaccording to a color component, also includes four transformation units.That is, the luma component coding unit 1700 includes four lumacomponent transformation units 1702, 1704, 1706, and 1708, the firstchroma component coding unit 1710 includes four first chroma componenttransformation units 1712, 1714, 1716, and 1718, and the second chromacomponent coding unit 1720 includes four second chroma componenttransformation units 1722, 1724, 1726, and 1728.

Referring to FIG. 21, 1-bit coding unit pattern informationcorresponding to a coded depth is set for a group 1730 to which only theluma component coding unit 1700 of the second coding unit belongs.However, coding unit pattern information corresponding to a coding depthis not set for the first chroma component coding unit 1710 and thesecond chroma component coding unit 1720.

In this case, the coding unit pattern information output unit 1450 ofFIG. 16 outputs 1-bit coding unit pattern information corresponding tothe coded depth regarding the luma component coding unit 1700.Accordingly, the image data decoder 1540 of FIG. 17 checks the 1-bitcoding unit pattern information corresponding to the coded depthregarding the luma component coding unit 1700 and determines whetherencoded texture information is present in the luma component coding unit1700. If it is determined that the encoded texture information ispresent, then the image data decoder 1540 may check transformation unitpattern information of the luma component transformation units 1702,1704, 1706, and 1708, and perform inverse transformation ontransformation coefficients of the transformation units 1702, 1704,1706, and 1708 based on the checking result.

Alternatively, the image data decoder 1540 may check only transformationunit pattern information of the first chroma component transformationunits 1712, 1714, 1716, and 1718 and the second chroma componenttransformation units 1722, 1724, 1726, and 1728 and may perform aninverse transformation on transformation coefficients of thetransformation units 1712, 1714, 1716, 1718, 1722, 1724, 1726, and 1728based on the checking result, without checking coding unit patterninformation corresponding to a coded depth of the first chroma component1710 and the second chroma component 1720 of the second coding unit.

Referring to FIG. 22, 1-bit coding unit pattern informationcorresponding to a coded depth is set for a group 1740 to which a lumacomponent coding unit 1700, a first chroma component coding unit 1710,and a second chroma component coding unit 1720 of a second coding unitbelong. In this case, the coding unit pattern information output unit1450 of FIG. 16 outputs the 1-bit coding unit pattern informationcorresponding to a coded depth for the second coding unit.

Referring to FIG. 23, 1-bit coding unit pattern informationcorresponding to a coded depth is set for each of a group 1750 to whicha luma component coding unit 1700 of a second coding unit belongs, agroup 1760 to which a first chroma component coding unit 1710 of thesecond coding unit belongs, and a group 1770 to which a second chromacomponent coding unit 1720 of the second coding unit belongs. In thiscase, the coding unit pattern information output unit 1450 of FIG. 16outputs a 3-bit coding unit pattern information corresponding to a codeddepth for the second coding unit.

The image data decoder 1540 of FIG. 17 may determine whether encodedtexture information is present in a coding unit by checking either 1-bitcoding unit pattern information corresponding to the coded depth (seeFIG. 22) or 3-bit coding unit pattern information corresponding to thecoded depth (see FIG. 23), for the second coding unit. If it isdetermined that the encoded texture information is present, then theimage data decoder 1540 may check transformation unit patterninformation of transformation units corresponding to the coding unit andperform an inverse transformation on transformation coefficients of thetransformation units based on the checking result.

FIGS. 24 to 26 illustrate coding unit pattern information correspondingto a coded depth when a coding unit corresponding to the coded depthincludes a plurality of transformation units, according to exemplaryembodiments. Referring to FIGS. 24 to 26, third coding unit of colorimage data according to the YCbCr standards includes a luma componentcoding unit 1800, a first chroma component coding unit 1820, and asecond chroma component coding unit 1830.

If the third coding unit includes at least four transformation units,then the luma component coding unit 1800 of the third coding unit alsoincludes at least four transformation units. That is, the number oftransformation units of the luma component coding unit 1800 is equal tothe number of transformation units of the third coding unit. Forexample, if the third coding unit includes sixteen transformation units,then the luma component coding unit 1800 also includes sixteen lumacomponent transformation units 1801, 1802, 1803, 1804, 1805, 1806, 1807,1808, 1809, 1810, 1811, 1812, 1813, 1814, 1815, and 1816.

Each of the first chroma component coding unit 1820 and the secondchroma component coding unit 1830 may include four transformation units.That is, the first chroma component coding unit 1810 may include fourfirst chroma component transformation units 1822, 1824, 1826, and 1828,and the second chroma component coding units 1830 may include foursecond chroma component transformation units 1832, 1834, 1836, and 1838.

One unit of coding unit pattern information corresponding to a codeddepth may be set as coding unit pattern information corresponding to acoded depth for a part of the luma component coding unit 1800, for agroup to which a predetermined number of luma component transformationunits belong. For example, coding unit pattern information correspondingto a coded depth may be set for each of groups to which four lumacomponent transformation units of the luma component coding unit 1800belong. That is, in the luma component coding unit 1800, 1-bit codingunit pattern information may be set for each of a group 1840 to whichfour transformation units 1801, 1802, 1803, and 1804 belong, a group1850 to which four transformation units 1805, 1806, 1807, and 1808belong, a group 1860 to which four transformation units 1809, 1810,1811, and 1812 belong, and a group 1870 to which four transformationunits 1813, 1814, 1815, and 1816 belong.

Referring to FIG. 24, coding unit pattern information corresponding to acoded depth is not set for the first chroma component coding unit 1820and the second chroma component coding unit 1830.

In this case, the coding unit pattern information output unit 1450 ofFIG. 16 outputs 4-bit coding pattern information corresponding to thecoded depth for the groups 1840, 1850, 1860, and 1870 of the lumacomponent coding unit 1800. The image data decoder 1540 of FIG. 17checks the 4-bit coding pattern information corresponding to the codeddepth, and determines whether encoded texture information is present foreach of the groups 1840, 1850, 1860, and 1870.

Alternatively, the image data decoder 1540 may check transformation unitpattern information of the first chroma component transformation units1822, 1824, 1826, and 1828 and the second chroma componenttransformation units 1832, 1834, 1836, and 1838 without checking patterninformation corresponding to the coded depth for the first chromacomponent 1820 and the second chroma component coding unit 1830.

Referring to FIG. 25, in a third coding unit, 1-bit coding unit patterninformation corresponding to a coded depth is set for each of aplurality of luma component coding unit groups 1840, 1850, 1860, and1870, a group 1880 to which a first chroma component coding unit 1820belongs, and a group 1885 to which a second chroma component coding unit1830 belongs. In this case, the coding unit pattern information outputunit 1450 of FIG. 16 outputs 6-bit coding unit pattern informationcorresponding to the coded depth, for the third coding unit.

Referring to FIG. 26, in a third coding unit, 1-bit coding unit patterninformation corresponding to a coded depth is set for each of aplurality of luma component coding unit groups 1840, 1850, 1860, and1870, and a group 1890 to which a first chroma component coding unit1820 and a second chroma component coding unit 1830 belong. In thiscase, the coding unit pattern information output unit 1450 of FIG. 16outputs 5-bit coding unit pattern information corresponding to the codeddepth, for the third coding unit.

The image data decoder 1540 of FIG. 17 determines whether encodedtexture information is present for the coding unit by checking eitherthe 6-bit coding unit pattern information corresponding to the codeddepth (see FIG. 25) or the 5-bit coding unit pattern informationcorresponding to the coded depth (see FIG. 26) for the third codingunit. If it is determined that the encoded texture information ispresent, the image data decoder 1540 may check transformation unitpattern information of a transformation unit included in the codingunit, and perform an inverse transformation on transformationcoefficients of the transformation units based on the checking result.

As described above, according to one or more exemplary embodiments,coding unit pattern information may be set for each of color components,and a plurality of pieces of coding unit pattern information of the samecoding unit, which are categorized according to a color component, maybe combined and encoded.

In a video encoding apparatus 100 and a video decoding apparatus 200according to exemplary embodiments, a plurality of pieces of coding unitpattern information that are categorized according to a color componentmay be encoded or decoded in an integrated manner, based on therelationship among coding unit pattern information regarding a lumacomponent, first chroma component, and second chroma component of thesame coding unit and the relationship among coding unit patterninformation of the same color component regarding neighboring codingunits.

For example, for variable-length coding (VLC) of a current coding unit,coding unit pattern information regarding a luma component, coding unitpattern information regarding a first chroma component, and coding unitpattern information regarding a second chroma component may be combinedand encoded using one codeword.

Furthermore, by way of example, a VLC table may be set in such as mannerthat different unary codewords correspond to combinations of a pluralityof pieces of coding unit pattern information, which are categorizedaccording to a color component, respectively. Accordingly, the pluralityof pieces of coding unit pattern information may be encoded in anintegrated manner. A VLC table may be selected in such a manner that theshorter a unary codeword, the higher probabilities of the combinationsof the plurality of pieces of coding unit pattern information.

As described above, it is possible to improve encoding efficiency byencoding or decoding a plurality of pieces of coding unit patterninformation, which are categorized according to a color component, in anintegrated manner, based on the relationship among a plurality of piecesof coding unit pattern information of the same coding unit that arecategorized according to a color component and the relationship among aplurality of pieces of coding unit pattern information of the same colorcomponent of neighboring coding units.

According to an exemplary embodiment, coding unit pattern informationcorresponding to a coded depth is set in a coding unit corresponding tothe coded depth, hierarchical coding unit pattern information is set intransformation units according to transformation depths, which aredivided from the coding unit corresponding to the coded depth, andtransformation unit pattern information is set in a final transformationunit.

Thus, the coding unit pattern information corresponding to the codeddepth, the hierarchical coding unit pattern information, and thetransformation unit pattern information may be defined continuously,based on the hierarchical structures of a coding unit and atransformation unit according to an exemplary embodiment.

Accordingly, in the video encoding apparatus 100 and the video decodingapparatus 200 according to exemplary embodiments, it is possible todetermine whether a texture component that is not 0 and that is includedfrom a coding unit to a transformation unit has been encoded by usingone piece of data unit pattern information that is hierarchically setaccording to a transformation depth, without differentiating the codingunit pattern information corresponding to the coded depth, thehierarchical coding unit pattern information, and the transformationunit pattern information from one another.

FIG. 27 is a diagram illustrating hierarchical coding unit patterninformation according to an exemplary embodiment. Referring to FIG. 27,transformation units 1912, 1914, 1916, 1918, 1920, 1930, 1942, 1944,1946, 1948, 1954, 1956, and 1958, the sizes of which are determinedaccording to corresponding transformation depths, respectively, are setfor a maximum coding unit 1900.

For example, a transformation unit corresponding to the transformationdepth of 0 is equal to the maximum coding unit 1900 in size, though themaximum coding unit 1900 illustrated in FIG. 27 does not include thetransformation unit corresponding to the transformation depth of 0.

The transformation units 1920 and 1930 are equal to the result ofsplitting the height and width of the transformation unit correspondingto the transformation depth of 0 into two equal parts, and correspond toa transformation depth of 1. Similarly, the transformation units 1912,1914, 1916, 1918, 1954, 1956, and 1958 correspond to a transformationdepth of 2, and transformation units 1942, 1944, 1946, and 1948correspond to a transformation depth of 3.

The hierarchical coding unit pattern information indicates whetherhierarchical coding unit pattern information regarding a lowertransformation depth is to be encoded. Furthermore, the hierarchicalcoding unit pattern information may reveal whether texture informationof the lower transformation depth has been encoded.

The maximum coding unit 1900 does not include the transformation unitcorresponding to the transformation depth of 0, and uses textureinformation of a transformation unit corresponding to the transformationdepth of 1 which is lower than the transformation depth of 0. Thus,1-bit hierarchical coding unit pattern information 1960 is set for thetransformation depth of 0.

Regarding the transformation depth of 1, the transformation unit 1920and the 1930 are decoded in the transformation depth of 1, and thus,texture information of a transformation unit corresponding to thetransformation of depth 2 which is lower than the transformation depthof 1 may not be encoded. Also, hierarchical coding unit patterninformation regarding the transformation depth of 2 may not be set.Thus, 1-bit hierarchical coding unit pattern information regarding thetransformation depth of 1, which indicates that texture information ofhierarchical coding unit pattern information regarding thetransformation depth of 2 may not be encoded, is provided for each ofthe transformation units 1920 and 1930.

However, texture information of a transformation unit corresponding tothe transformation depth of 2 which is lower than the transformationdepth of 1 is to be encoded for each of a group, corresponding to thetransformation depth of 1, to which the transformation units 1912, 1914,1916, and 1918 corresponding to the transformation depth of 2 belong,and a group, corresponding to the transformation depth of 1, to whichthe transformation units 1942, 1944, 1946, 1948, 1954, and 1956, and1958 belong. Thus, coding unit pattern information regarding thetransformation depth of 2 may be encoded, and 1-bit hierarchical codingunit pattern information regarding the transformation depth of 1 may beset for each of the groups so as to indicate this fact.

Accordingly, a total of 4-bit hierarchical coding unit patterninformation 1970 is set for the transformation depth of 1.

Regarding the transformation depth of 2, the transformation units 1912,1914, 1916, 1918, 1954, 1956, and 1958 may be decoded in thetransformation depth of 2. For this reason, texture information of atransformation unit corresponding to the transformation depth of 3 whichis lower than the transformation depth of 2 may not be encoded, andthus, hierarchical coding unit pattern information regarding thetransformation depth of 3 may not be set. Thus, 1-bit hierarchicalcoding unit pattern information regarding the transformation depth of 2may be set for each of the transformation units 1912, 1914, 1916, 1918,1954, 1956, and 1958 so as to indicate that hierarchical coding unitpattern information regarding the transformation depth of 3 may not beencoded.

However, information of a transformation unit corresponding to thetransformation depth of 3 may be encoded for a group, corresponding tothe transformation depth of 2, to which the transformation units 1942,1944, 1946, and 1948 belong. Thus, the coding unit pattern informationregarding the transformation depth of 3 may be encoded, and 1-bithierarchical coding unit pattern information regarding thetransformation depth of 2 may be set so as to indicate this fact.

Accordingly, a total of 8-bit hierarchical coding unit patterninformation 1980 may be set for the transformation depth of 2.

The transformation depth of 3 is a final transformation depth, andtherefore, 1-bit hierarchical coding unit pattern information regardingthe transformation depth of 3 may be set for each of the transformationunits 1942, 1944, 1946, and 1948 so as to indicate that hierarchicalcoding unit pattern information regarding a lower transformation depthmay not be encoded. Thus, a total of 4-bit hierarchical coding unitpattern information 1990 may be set for the transformation depth of 3.

FIG. 28 is a flowchart illustrating a method of encoding video data byusing coding unit pattern information, according to an exemplaryembodiment. Referring to FIG. 28, in operation 2010, a current pictureis split into at least one maximum coding unit. In operation 2020, acoded depth to output a final encoding result according to at least onesplit region, which is obtained by splitting a region of each of the atleast one maximum coding unit according to depths, is determined byencoding the at least one split region, and a coding unit according to atree structure is determined.

In operation 2030, a result of encoding image data according to onecoded depth for each of the at least one maximum coding unit, and aresult of encoding information regarding the coded depth and an encodingmode are output.

Coding unit pattern information corresponding to a coded depth, whichindicates whether texture information of coding units according to codeddepths of the at least one maximum coding unit has been encoded, may beencoded as coding unit pattern information of the at least one maximumcoding unit. If hierarchical coding unit pattern information ishierarchically encoded according to a transformation depth, then each ofa plurality of pieces of hierarchical coding unit pattern informationcorresponding to transformation depths indicates whether thehierarchical coding unit pattern information regarding a transformationdepth that is lower than the corresponding transformation depth has beenencoded.

FIG. 29 is a flowchart illustrating a method of decoding video data byusing coding unit pattern information, according to an exemplaryembodiment. Referring to FIG. 29, in operation 2110, a bitstream ofencoded video is received and parsed.

In operation 2120, image data of a current picture assigned to at leastone maximum coding unit, information regarding a coded depth of a codingunit according to a tree structure for each of the at least one maximumcoding unit, and information regarding an encoding mode, are extractedfrom the parsed bitstream. Also, the coding unit pattern informationindicating whether texture information of a maximum coding unit has beenencoded is extracted on a basis of the at least one maximum coding unit.Coding unit pattern information corresponding to a coded depth regardingcoding units according to coded depths of each maximum coding unit, andhierarchical coding unit pattern information may be extracted as codingunit pattern information of the at least one maximum coding unit.

In operation 2130, encoded image data corresponding to the at least onemaximum coding unit is decoded, based on the coded depths of the atleast one maximum coding unit, information regarding an encoding mode,and information regarding the coding unit pattern information, therebyreconstructing the image data. It is possible to determine whethertexture information of the coding unit corresponding to the coded depthhas been encoded based on the coding unit pattern informationcorresponding to the coded depth. Also, it is possible to determinewhether the hierarchical coding unit pattern information regarding alower transformation depth has been encoded based on the hierarchicalcoding unit pattern information regarding each of the transformationdepths.

In the coding unit corresponding to the coded depth, data encoded in atransformation unit may be decoded by performing an inversetransformation on a transformation coefficient based on transformationunit pattern information of the transformation unit.

In general, in a related art video encoding/decoding method, a 16×16 or8×8 macroblock is used as a transformation unit when transformation orinverse transformation is performed on image data. Coded block patterninformation is encoded and transmitted on a macro block basis during anencoding process, and is used for a decoding process.

In contrast, according to the above-described exemplary embodiments,coding unit pattern information based on a hierarchically structuredcoding unit and transformation unit is used. Thus, the coding unitpattern information may be encoded in a coding unit which is greaterthan a macroblock or is a variously sized data unit. Also, the codingunit pattern information may be encoded in a coding unit, which includesa plurality of hierarchical structured transformation units according toa tree structure, in an integrated manner. Accordingly, the efficiencyof encoding/decoding and transmitting the coding unit patterninformation can be improved.

One or more exemplary embodiments may be embodied as a computer program.The computer program may be stored in a computer readable recordingmedium, and executed using a general digital computer. Examples of thecomputer readable medium include a magnetic recording medium (a ROM, afloppy disc, a hard disc, etc.), and an optical recording medium (aCD-ROM, a DVD, etc.).

While exemplary embodiments have been particularly shown and described,it will be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope of the present inventive concept as defined by theappended claims. The exemplary embodiments should be considered indescriptive sense only and not for purposes of limitation. Therefore,the scope of the present inventive concept is defined not by thedetailed description of exemplary embodiments, but by the appendedclaims, and all differences within the scope will be construed as beingincluded in the present inventive concept.

What is claimed is:
 1. A video decoding apparatus comprising: anextractor which extracts from a bitstream transformation indexinformation indicating whether a transformation unit of a current levelincluded in a current coding unit is split; a decoder which splits thetransformation unit of the current level into transformation units of alower level when the transformation index information indicates a splitof the transformation unit of the current level, wherein the extractorfurther extracts pattern information for the transformation unit of thecurrent level when the transformation index information indicates anon-split of the transformation unit of the current level, wherein thepattern information indicates whether the transformation unit of thecurrent level contains one or more transform coefficients not equal to0.
 2. The video decoding apparatus of claim 1, wherein thetransformation unit of the current level is included in the coding unit,and a size of the transformation unit of the current level is smallerthan or equal to a size of the coding unit.
 3. The video decodingapparatus of claim 2, wherein the transformation unit of the currentlevel is obtained by halving a height and a width of the coding unit. 4.The video decoding apparatus of claim 1, wherein the coding unit is adata unit in which a picture of the encoded video is encoded and thetransformation unit of the current level is a data unit in which thedata of the coding unit is transformed.